Effect of coordination anion substitutions on relaxation dynamics of defect dicubane Zn2Dy2 tetranuclear clusters

Abstract

We showcase the coordination anion substitution effect on the relaxation dynamics of defect dicubane Zn₂Dy₂ tetranuclear clusters. On utilization of the coordination similarity of acetate and nitrate anions, we successfully isolated two defect dicubane Zn₂Dy₂ tetranuclear clusters with formulas [Zn₂Dy₂(L)₄(NO₃)₂(CH₃OH)₂]·2CH₃COCH₃ (1) and [Zn₂Dy₂(L)₄(CH₃COO)₂(CH₃CH₂OH)₂]·4CH₃COCH₃ (2), where L denotes the fully deprotonated H₂L ligand (E)-4-(tert-butyl)-2-((2-hydroxy-3-methoxybenzylidene)amino)phenol. Such a subtle change in the coordination anion around the Dy^III site imposes a significant effect on the distinct relaxation dynamics in 1 and 2. Their magnetic properties were characterized through SQUID magnetometry and theoretical calculations to determine the effective energy barrier, energy levels, magnetic anisotropy and intracluster magnetic exchange coupling interactions. Both tetramers display frequency dependence of the out-of-phase ac magnetic susceptibility signal under zero applied dc field associated with single-molecule magnetic behaviour. The effective energy barriers of 1 and 2 are 108 and 40 cm⁻¹, respectively. Theoretical calculations suggest that the different relaxation dynamics between them are mainly ascribed to the variation of the coordination anion around the Dy^III site.